Local sources said the girl had been accused of illicit relations with a man and that the flogging took place about a month and a half ago.

Since then, the provincial government in the North West Frontier Province agreed to implement Sharia law as part of a peace deal with militants there.

A press release quoted Chief Justice Chaudhry - who was only recently restored to office - as saying the action was a cruel violation of fundamental rights that gave Pakistan a bad name.

Forced to marry

The language in the video is of the Swati dialect of Pashto, says the BBC's Abdul Hai Kakar.

The burka-clad woman is heard crying throughout the two-minute flogging and at one point swears on her father that she will not do it again.

Relatives of the man involved in the incident told the BBC he had gone to the house of the girl in the village of Kala Kalay to do repairs as an electrician, but militants accused him of having a relationship with her.

They dragged him from the house and flogged him before punishing the girl, his relatives said.

The Taleban made the girl's brother hold her down during the flogging, they said.

After the incident, the Taleban forced the couple to marry and instructed the man not to divorce his wife. His relatives say he has been left mentally scarred.

The incident happened weeks before the new Sharia courts began to be introduced in Swat.

Militants 'still in control'

Prime Minister Gilani said he strongly condemned the "shameful" incident in a statement issued by his office.

Mr Gilani said it was contrary to Islamic principles, which teach Muslims to treat women politely and gently.

He said the government believed in the rights of women and would continue to take every measure to protect their rights.

The Sharia system was agreed in Swat to try to stop the Taleban from imposing their harsh brand of justice, the BBC's Islamabad correspondent Barbara Plett says.

Previously they had beheaded dissidents and killed women accused of un-Islamic behaviour.

That seems to have significantly decreased after the Taleban leader officially accepted the Islamic courts.

However, it is not clear whether this new justice system will replace Taleban rule in practice.

The courts seem to be operating with some effect in Swat's main city of Mingora but not in outlying rural areas.

There witnesses say the militants continue to exercise control, if not as brutally as before.